Pressure sensitive copying paper

ABSTRACT

An excellent pressure sensitive copying sheet is provided by applying as a color former certain encapsuled fluoran compounds, i.e., fluoran compounds linking in the 7-position with at least one of the two nitrogen atoms in a piperazine ring and having a dialkylamino group in the 3-position to either a single sheet or to the upper leaf of a pressure sensitive paper. The color former is soluble in aromatic solvents and also has excellent light fastness.

United States Patent [191 Terayama et al.

[ Oct. 29, 1974 PRESSURE SENSlTIVE COPYING EAPER Inventors: Mutsuo Terayama; Kenji Yamamoto, both of Oosaka, Japan Assignee: Yamamoto Kagaku Gosei Kabnshiki Kaisha, Osaka, Japan Filed: Nov. 29, 1972 Appl. No.: 310,586

Related US. Application Data Division of Ser. No. 208,432, Dec. 15, 1971.

Foreign Application Priority Data Dec. 15, 1970 Japan 45-112052 US. Cl 117/362, 117/368, 260/268 PC, 260/268 TR, 260/335 Int. Cl. 1341c 1/06, B4lm 5/00 Field 01 Search 260/335, 268 TR, 268 PC; ll7/36.2, 36.8

[56] References Cited UNITED STATES PATENTS 7 3,649,649 3/1972 Orita et al 260/343,3 3,669,711 6/1972 Kimura et al. 260/335 X 3,694,247 9/1972 Desjarlais 117/368 X Primary ExaminerThomas J. Herbert, Jr. Attorney, Agent, or Firm-Armstrong, Nikaido & Wegner [5 7] ABSTRACT 7 Claims, N0 Drawings PRESSURE SENSITIVE COPYING PAPER This is a division, of application Ser. No. 208,432, filed Dec. 15, 197i.

BACKGROUND OF THE lNVENTlON Basically, pressure sensitive copying sheet consists of two sheets of paper, an upper leaf and a lower leaf, the lower surface of the upper leaf being coated with minute capsules containing a color reactive achromatic substance (hereinafter called a color former") dissolved in a low volatile solvent and the upper surface of the lower leaf being coated with a solid acid, such as acid clay, zeolite, bentonite, attapulgite & phenolic compound, etc. When the lower surface of the upper leaf and upper surface of the lower leaf are put together and pressure is applied to the upper surface of the upper leaf by handwriting or typing, the capsules under pressure are broken and the color former contained therein is adsorbed by the solid acid on the upper surface of the lower leaf to develop a color, and thereby the object of copying is attained.

There is also a type of pressure sensitive copying sheet having a mechanism to develop a color when a regional pressure is exerted upon a sheet of paper holding capsules, which contain a color former, and a solid acid on or within it. However, such type is quite similar to the first-mentioned pressure sensitive copying paper (consisting of two sheets of paper, an upper and lower leaf) with respect to the mechanism of developing a color, and thus the same color former can be used for both types. And any of the above-mentioned facts belongs to the prior-known arts.

Conventionally, a number of compounds have been known to be useful as the color former, such as lactones, i.e, crystal violet lactone and malachite green lactone; thiazine compounds, i.e., benzoyl leucomethylene blue; and other leucoauramine and spiropyran compounds, and others.

In most of the pressure sensitive copying sheet now in practical use, crystal violet lactone and benzoyl leucomethylene blue, both of which develop a blue color, are used as the main color former. But the blue image due to these color formers is not suitable for recopying by zerox or diazo system. It has therefore been hoped for to find out some solution for this defect.

This defect can be solved by obtaining a black image in two ways: (1) to employ a black color former, or (2) to employ two or more color formers in combination for synthesizing a black image.

SUMMARY In accordance with the invention, an excellent pressure sensitive copying paper can be obtained by using a new and novel color fomer which is very advantageous in obtaining a black image, offering superiority not only in the speed of color development, the shade, and the light resistance of the color developed, and the solubility but also in the simplicity of the manufacturing method and the low cost. The new and novel color former used in the present invention all develop into either black or red. One which develops into black can be used alone, while the other which develops into red can advantageously produce a highly stabilized black image when mixed with one other color former which develops into green (for example, 3-diethylamino-7- benzylaminofluoran (See Canadian Pat. No. 8l4,948)).

The coloraformer used in the present invention can be represented by the following general formulae (1) 5 and (ll).

wherein R R and R represent methyl or ethyl, and R and R represent hydrogen, methyl group, or halogen.

wherein R,,R R and R are the same as in the general formula (I).

That is to say, we have found that the fluoran compounds linking in the 7-position with at least one of the two nitrogen atoms in a piperazine ring and having a dialkylamino group in the 3-position can become the black and red color formers which are distinguished in all of the color developing speed, the shade and the light resistance of the color developed and the solubility and that they can be readily synthesized by the process shown by the following reaction formula.

on B2 l O O OH wherein R R R R and R are the same as in the general formula (I).

(III) can be prepared with much ease by the follow ing reaction formula. (See Beilstein, Hauptwerk, vol. 5 23, 11

(III) a CO DETAILED DESCRIPTION i This compound lvj is a white crystal obtained condensing 2 parts of ortho-(4-diethylamino-2-hydroxybenzoyl)benzoic acid (V) and 3 parts of N, N- di(paramethoxyphenyl)piperazine (VI) in concentrated sulfuric acid and having a melting point of 237 to 240C. It has the characteristics which are highly advantageous for the preparation of the pressure sensitive copying sheet, such as the rapid development into a black or blackish red color in the presence of a solid acid, and the excellent light resistance of the color developed as well as the high solubility in the solvent.

The compound (Vl) can be readily obtained by refluxing under heat paraanisidine and dibromoethane in the presence of sodium carbonate.)

N, N-bls (3-dietllylaminolluoranyl) piperazine (VII) (VII) (Vlllis a white crystal obtained condensing 4 parts of (V) and 3 parts of (VI) in concentrated sulfuric acid and having a melting point of 265 to 270C. It also has the characteristics which are highly advantageous for the preparation of the pressure sensitive copying sheet, such as the rapid development into a black or blackish red color in the presence of solid acid, and the excellent light resistance of the color developed as well as the high solubility in the solvent.

(Vlll) is a white crystal obtained by condensing 2 parts of (V) and 1 part of (VI) in concentrated sulfuric acid and having a melting point of 210 to 215C. This also rapidly develops into a dark red color in the presence of a solid acid, has an excellent light resistance after developing into a color, and dissolves well in the solvent.

The present invention is further illustrated by the following examples.

Example 1 g of gelatin and 60 g of gum arabic were dissolved in 50 ml of water of 40C. On the other hand, 4 g of 3- diethylamino-7-(N'-paramethoxyphenyl)piperazinofluoran (IV) was dissolved in 120 g of diphenyl chloride, and then this solution was added to the abovementioned aqueous solution of gelatin and gum arabic and perfectly dispersed into an emulsion by a homomixer. Water of 50C. was added until its volume became 2,000 ml in total, followed by ml of 10 per cent acetic acid. While stirring, water of 50C was further added until the total weight became 4 kg, and the stirring was continued for a period of an hour. While still stirring, the solution was cooled down to below 10C with ice water, and 10 per cent caustic soda was added until a pH of 9, was reached, and gradually returned to room temperature. The product was applied onto the lower surface of the upper leaf and dried. On the other hand, a solid acid such as acid clay or phenolic compounds, etc. was applied onto the upper surface of the lower leaf.

When copying was carried out with the upper and lower leaves thus prepared, a black or blackish red image rapidly developed, which showed an excellent light resistance.

Example 2 Example 3 1.0 g of N,N-bis( 3 -diethylamino-6 methylfuloranyl) piperazine (VIII) and 2.5 g of 3- diethylamino-7-benzylaminofluoran (See Canadian Pat. No. 814,948) were dissolved in 120 g of diphenyl chloride, which solution was then treated in the same 5 way as in Example 1 to obtain the pressure sensitive copying sheet. When copying was carried out with this copying sheet, a black image rapidly developed, which showed an excellent light resistance.

Example 4 4 g of N,N'-bis(3'-diethylaminofluoranyl)piperazine (VI!) was dissolved in 120 g of diphenyl chloride. By treating this in the same way as in Example 1, an aqueous dispersion of minute capsules was obtained. This was sprayed and dried into a powder of minute capsules, which was mixed with and dispersed in a 4 per cent xylene solution of p-phenylphenolformaldehyde condensate. And this dispersed solution was applied onto a sheet of paper and dried. When a regional pressure was exerted on this coated sheet of paper, it immediately developed a black image, which showed an excellent light resistance.

Example 5 4 of N,N '-bis( 3 '-diethylamino-6 methylfluoroanyl) piperazine (Vlll) was dissolved in 120 g of diphenyl chloride.

By treating this solution in the same way as in Example 1, an aqueous dispersion of minute capsules was obtained. This was mixed with 8 g of fine powder of p-phenylphenolformaldehyde condensate to disperse the latter therein, and 40 g of pulp was further added thereto. Then the dispersion was diluted with water until the final solid content became 0.5 per cent. Then the product was run onto a Fourdrinier screen to be made into a sheet of paper. When a regional pressure was exerted on this sheet of paper, it immediately developed a black image with an excellent light resistance.

Although diphenyl chloride was used as a solvent in the foregoing examples, the same pressure sensitive copying paper can be obtained without problem with the use of other aromatic solvent. These aromatic solvents of low volatility include lower alkyl diphenyls, such as methyl-, ethyland propyl diphenyl, and higher alkyl benzenes, such as dodecyl-, decyland octyl benzene, having a boiling point of above 150C. If the boiling point of the solvent is al least 150C, it has sufficient low volatility according to the invention.

The solid acid functions as an electron acceptive adsorbent. In place of those used in the previous examples zeolite, bentonite, attapulgite and Silton (manufactured and saled by Mizusawa Chemical Company Ltd.) can be used with excellent results.

What is claimed is:

l. in a pressure sensitive copying paper, a paper sheet having applied thereto at least one fluoran compound of the formula:

wherein each of R and R is methyl or ethyl, each of R and R is hydrogen, methyl or halogen; and A is either wherein R is methyl or ethyl; and

R R R and R are as defined above.

2. Pressure sensitive copying paper according to claim 1 comprising an upper leaf having said fluoran compound applied thereto, said compound being dissolved in a solvent of low volatility and the resulting solution being packed in minute capsules, and a lower leaf having applied thereto a solid acid.

3. Pressure sensitive copying paper according to claim 1 in which a single sheet of paper has applied thereto said fluoran compound, said compound being dissolved in a solvent of low volatility and the resulting solution being packed in a minute capsules, and a solid acid.

4. The pressure sensitive copying paper of claim 1 wherein in said fluoran compound R and R are hydrogen or methyl.

5. Pressure sensitive copying sheet according to claim 1 wherein the fluoran compound is 3- diethylamino-7-(N'-paramethoxyphenyl) piperazinofluoran.

6. Pressure sensitive copying sheet according to claim 1 wherein the fluoran compound is N,N'-bis(3- diethylaminofluoranyl) piperazine.

7. Pressure sensitive copying sheet according to claim 1 wherein the fluoran compound is N,l I'-bis(3- diethylamino 6'-methylfluoranyl)piperazine. 

1. IN A PRESSURE SENSITIVE COPYING PAPER, A PAPER SHEET HAVING APPLIED THERTO AT LEAST ONE FLUORAN COMPOUND OF THE
 2. Pressure sensitive copying paper according to claim 1 comprising an upper leaf having said fluoran compound applied thereto, said compound being dissolved in a solvent of low volatility and the resulting solution being packed in minute capsules, and a lower leaf having applied thereto a solid acid.
 3. Pressure sensitive copying paper according to claim 1 in which a single sheet of paper has applied thereto said fluoran compound, said compound being dissolved in a solvent of low volatility and the resulting solution being packed in a minute capsules, and a solid acid.
 4. The pressure sensitive copying paper of claim 1 wherein in said fluoran compound R3 and R4 are hydrogen or methyl.
 5. Pressure sensitive copying sheet according to claim 1 wherein the fluoran compound is 3-diethylamino-7-(N''-paramethoxyphenyl) piperazinofluoran.
 6. Pressure sensitive copying sheet according to claim 1 wherein the fluoran compound is N,N''-bis(3''-diethylaminofluoranyl) piperazine.
 7. Pressure sensitive copying sheet according to claim 1 wherein the fluoran compound is N,N''-bis(3''-diethylamino 6''-methylfluoranyl)piperazine. 